The present invention relates to a portable radio communication apparatus and, more particularly, to such an apparatus having a diversity reception function.
An example of portable radio communication apparatus of the foregoing type is disclosed in "No. 2455: Study on a Diversity Antenna for Portable Radio Unit" by Taga et al, National Convention (Record) of the Institute of Electronics and Communication Engineers of Japan, pp. 10-155, 1984. The communication apparatus disclosed in this paper includes two folded, inverted F-type antennas which are built in a housing, so that diversity reception may be performed through those antennas. Although such construction is suitable for portable apparatus design, it fails to achieve a requisite degree of antenna gain.
A portable radio communication apparatus capable of attaining sufficient gain is disclosed in a Japanese unexamined laid-open patent application entitled "Portable Radio," No. Sho No. 62-49729, namely, 49729 of 1987 by Hashiomoto et al. which is assigned to the assignee of the instant application (Corresponding patent applications are: U.S. Ser. No. 897,989; European Ser. No. 86306575.1; Canadian, Ser. No. 516,870-8; and Australian, Ser. No. 61837/86.). As will be described in detail later, the apparatus of the foregoing Japanese application is provided with a single sleeve or whip antenna and a single built-in antenna for effecting diversity reception. The sleeve or whip antenna is connected to both a transmitter and a diversity receiver while the built-in antenna is connected to the diversity receiver. The sleeve or whip antenna may be tucked away in a housing to enhance portability. So long as the apparatus is used with the sleeve or whip antenna pulled out of the housing, sufficiently high reception and transmission gains are assured due to the high antenna gain and diversity gain of the sleeve or whip antenna. However, once the sleeve or whip antenna is retracted into the housing, the transmitter becomes substantially inoperable and makes bidirectional communication impractical.